The present invention relates to the suspension of vehicles. It relates both to the guidance of a vehicle wheel relative to the chassis of this vehicle and to the control of the deflection of the wheel relative to the chassis.
It is known that a wheel is mounted on a hub, and that the hub is mounted on a wheel carrier by means of a rolling bearing embodying the axis of rotation of the wheel. The guidance of the wheel involves allowing the wheel carrier to be displaced relative to the vehicle by an amount sufficient for the suspension of the vehicle. At the same time, the guidance of the wheel must be such that the path of the vehicle is controlled as strictly as possible. The deflecting movement which is sought is to a great extent in the vertical direction. It may be desirable to allow slight movement in the longitudinal direction, while, ideally, the aim is to avoid any relative movement in the transverse direction. Furthermore, the steering and the variations in camber which all these movements may induce must be strictly contained, thus also resulting in a design constraint which the average person skilled in the art must take into account.
If the "plane" of the wheel refers to the plane perpendicular to the axis of rotation of the wheel and passing through the middle of the wheel or, more specifically, through the center of the area of contact with the ground of a tire or of an elastic casing mounted on said wheel, the control of the deflecting movements is tantamount to stating that guidance must ensure a strictly controlled position of the plane of the wheel relative to the chassis.
In addition to the aspect of the guidance of the plane of the wheel, the suspension must also ensure that the vehicle load is transferred to the wheel and that the amplitude. of the movements allowed by the guidance is controlled. This is conventionally the function of the springs and shock absorbers or of the members combining the spring function (flexibility) and the damping function (preventing oscillations from being maintained).
All the suspensions used at the present time on vehicles have in common the characteristic of being somewhat bulky. The suspension arms must be of some length, so that their angular movement is not accompanied, for example, by excessive track variations (suspension diagrams). Even the MacPherson strut, of which the increasing use is known to be due to the greater space which it leaves for installing an engine unit in the transverse position, has its share of disadvantages, including its large overall height.
Moreover, the search for an even better compromise between suspension comfort and roadholding leads to the provision of so-called active or semi-active suspensions, the operation of which is now made possible by advances in electronics. In general, the result of this is that the installation of the suspension on the vehicle takes up even more space by increasing the bulk of the springs and/or shock absorbers, or even by adding additional members forming a spring or shock absorber.